Which is example of the Simple Myopic Astigmatism among the prescriptions given below:
**Core Concept**
Simple Myopic Astigmatism is a type of refractive error characterized by a combination of myopia (nearsightedness) and astigmatism. It occurs when the eye has an irregularly shaped cornea that prevents light from focusing properly on the retina, resulting in blurred vision at all distances.
**Why the Correct Answer is Right**
Astigmatism is often caused by an irregular curvature of the cornea or lens inside the eye. In Simple Myopic Astigmatism, the degree of myopia is less than 1.00 diopter. The prescription for Simple Myopic Astigmatism typically includes two spherical powers with a minus sign, indicating a combination of myopia and astigmatism. The correct prescription for Simple Myopic Astigmatism is -1.50 -1.00 x 90, which indicates a -1.50 diopter of myopia in one meridian and a -1.00 diopter of astigmatism at a 90-degree axis.
**Why Each Wrong Option is Incorrect**
* **Option A:** No mention of astigmatism or a minus sign, indicating a simple myopic prescription.
* **Option B:** Presence of plus power, indicating hyperopia (farsightedness), not myopia.
* **Option C:** Presence of two plus powers, indicating hyperopia, not myopia or astigmatism.
* **Option D:** Presence of two minus powers with a different axis, indicating a compound myopic astigmatism, not simple myopic astigmatism.
**Clinical Pearl / High-Yield Fact**
When prescribing for astigmatism, the axis of the prescription is critical, as it determines the orientation of the corrective lens. A 90-degree axis indicates a vertical meridian, while a 180-degree axis indicates a horizontal meridian.
**Correct Answer: C. +2.00 +2.00 x 180**